The present invention relates to an ink jet recording method, a recording device and a data processing method in which high quality images can be formed on a recording material with suppressed banding nonuniformly, more particularly to the ink let recording method, the recording device and the data processing method in which the recording is carried out through one-path or multi-path printing.
The present invention is applicable to any equipment using as the recording material, paper, textile, leather, nonwoven fabric, OHP sheet, metal or the like. More particularly, the Present invention is applicable to a printer, coping machine, facsimile machine or another office equipment, industrial manufacturing machines or the like.
As regards the recording on the recording material using the recording apparatus, the demand for high-speed printing picks up. In order to increase the printing speed, it is one of the methods to refuse the number of paths in the multi-path printing which has been proposed to accomplish formations of high quality images. Here, the number of paths is the number of scans of the carriage required to complete one line of printing.
Since the number of ejection outlets of the recording head is limited, the amount of the sheet feed for units can is smaller if the number of paths is larger. On the other hand, the sheet feeding distance per unit can can be increased by reducing the number of paths. For example, in the case that printing is carried out in the two-path mode, the speed can simply be doubled by changing it to one-path printing. That is, the reduction of the number of paths reduces the number of scans to cover a predetermined area (one sheet, for example), and increases the distance of sheet feed, so that time required for printing is shortened.
In the case that recording ahead having a plurality of ejection outlets for ejecting the recording liquid (ink) scans the recording material in the direction perpendicular to the direction in which ejection outlets are arranged, an image is formed in an image area in the form of a band by one scan of the recording head, as shown in FIG. 21.
Thus, in the case of the one-path printing, the duty (ratio) of the recording ink ejected per unit time is larger than when the one band area is printed through a plurality of scans (multi-path printing). Therefore, the production of the black stripe between the adjacent bands (paths) is remarkable at the portions where the printing duty is high, although it is different depending on the nature of the recording material and the recording liquid.
The problem is more significant in the case of lateral arrangement of the recording heads in which cyan, magenta and yellow recording heads or the like are arranged in the main scan direction. This is because the boundaries appear at the same position. FIG. 6 schematically shows the laterally arranged recording heads.
The black stripe appearing at the adjacent bands is called connecting stripe, spending or the like. It might deteriorate the image to such an extent that image is practically unsatisfactory.
Therefore, a method of avoiding the banding in one-path printing, thus improving the image quality.
For example, Japanese Laid-open Patent Application 11-188898 discloses a serial scanning type in which a recording head repeatedly scans the recording material in the main scan direction to print the image band by band, and a method is used to avoid the production of a stripe at the connecting portion between the adjacent bands. More particularly, at least one of the first and the last raster lines of one band covered by one scan of the recording head is divided into a plurality of unit areas including predetermined dots. In accordance with the image data, more particularly, with a sum of an amount of ink ejection (duty) for a noting color in each of the divided areas and an amount of ink ejections for the other in the unit areas, the amount of the ink actually ejected is reduced (thinning).
The studies made by the inventors of the present invention have revealed that how conspicuous the boundary stripe is depends upon the printing duty at the band border, and is also significantly affected by the difference in ink depositing time between two adjacent bands. For example, if control is executed to increase the interval in terms of the time between two adjacent bands, in the middle of a printing operation, in order to prevent a recorded image from being smeared as a completed print is discharged, or to prevent a recording head from overheating, the boundary stripe, the position of which corresponds to the increased interval, becomes more conspicuous than the boundary stripes which occur when an image is printed at the normal speed or without an increased interval. Therefore, a process devised to deal with the boundary stripe without consideration of the aforementioned inter-band delay cannot satisfactorily reduce the conspicuousness of a boundary stripe; such a process has much to be improved regarding image quality.
Further, when the distance a carriage must travel to complete the scanning of each raster line is large, there is a significant amount of lag between the two ends of the each raster line. For example, when the speed of a carriage is 8 inches per second, it takes one second for the carriage to scan a single raster line of an image which covers the entirety of an A4 (8 inch) paper. Thus, when an image is bidirectionally printed, this lag becomes two seconds, significantly affecting the conspicuousness of the boundary stripe.
Accordingly, it is a principal object of the present invention to provide an ink jet recording apparatus, a recording method and a data processing method with which the banding is suppressed even if the interval in time between two adjacent bands is not constant.
Another object of the present invention is to provide an ink jet recording apparatus, a recording method, and a data processing method, which make it possible to provide an image, the banding of which is far less conspicuous than that of an image formed with the use of a combination of a conventional recording apparatus, a conventional recording method, and a conventional data processing method, even if the image is bidirectionally printed.
According to an aspect of the present invention, there is provided an ink jet recording apparatus for effecting recording on a recording material by ejecting ink through a plurality of ejection outlets in units of band with relative scanning movement between a recording head and the recording material, said ink jet recording apparatus, comprising obtaining means for obtaining scanning interval information relating to time period required for recording a connecting portion between a band of a certain scan of the recording bead and a band of the next scan of the recording head; and reducing means for reducing an amount of the ink shot to a neighborhood of the connecting portion on the basis of the scanning interval information obtained by said obtaining means.
According to another aspect of the present invention, there is provided an ink jet recording apparatus for effecting recording on a recording material by ejecting a plurality of ink droplets in units of band with relative scanning movement between a recording head and the recording material, said ink jet recording apparatus, comprising obtaining means for obtaining scanning interval information relating to time period required for recording a connecting portion between a band of a certain scan of the recording head and a band of the next scan of the recording head; and obtaining means for obtaining relative information indicative of a relation of amounts of inks shot in each of unit areas provided by dividing a neighborhood of a connecting portion between adjacent bands scanned by the recording head; determining means for determining, for each of the inks, a reduction rate at which an amount of the ink shot to the neighborhood of the connecting portion in the unit area, on the basis of the relative information for each of the unit areas obtained by said obtaining means and amount information indicative of the amount of each of the inks shot to the unit area; reducing means for reducing the amount of the ink shot to the neighborhood of the connecting portion at the reduction rate determined by said determining means when a scanning interval time period indicated by the scanning interval information obtained by said obtaining means is not less than a predetermined time period.
With the provision of the above described structural arrangement, even when the scanning interval in time between the two adjacent bands is not constant, an image, the boundary stripes of which are substantially less conspicuous than those of an image formed with the use of a conventional means, can be obtained, by thinning the recording data for the adjacencies of the boundary, on the basis of the information regarding the scanning interval in time between two adjacent bands.
Further, the color designation for each unit area (specific area) in terms of color area (combination of hue and chromaticity) is determined on the basis of the number of the recording data (number of ink dots to be placed) for each unit area adjacent to the boundary, and the thinning level for each unit area can be set for each ink and each unit area, on the basis of the thus determined color designation for each unit area. The thinning process is carried out for each ink, on the basis of the thus set thinning level. As a result, the conspicuousness of a boundary stripe which is generated between adjacent two portions of an image, correspondent to two primary scanning movements of a recording head across two adjacent raster lines, when an image is formed by a single-pass printing operation.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.